1. Field of the Invention
The present invention relates to an internal combustion engine and, more particularly, to a breathing device used in the engine to relieve an internal pressure inside a crankcase.
2. Description of the Prior Art
A breathing device is known as a device which, when an internal pressure inside a crank chamber increases as a result of movement of a piston under suction and expansion strokes, operates to suck a blow-by gas from the crank chamber and then introduce it into a rocker arm chamber and also, if necessary, to circulated the blow-by gas towards an inside of an air cleaner. The breathing device is generally provided with an oil separation mechanism for separating an oil component from the blow-by gas during circulation of the blow-by gas. This oil separation mechanism generally includes an oil separation chamber and a check valve both disposed inside a rocker cover mounted atop a cylinder head of the engine.
However, in the breathing devices, since the structure is complicated and the number of component parts is relatively large, the cost of assembling is high and the design limitation is stringent. Also, while the check valve must have a sufficient response to opening or closing and a sufficient sealability in order to secure the performance, the check valve tends to become bulky in order to fulfill the requirements, resulting in increase in size of the engine.
The engine with the check valve disposed inside the crank case is also known, but even this engine has problems similar to those discussed above.
In view of the foregoing, the present invention is intended to provide an improved breathing device for a combustion engine, wherein the structure around the check valve is simplified so that the engine as a whole can be manufactured compact.
To this end, the present invention provides a breathing device for an internal combustion engine which includes a check valve for fluid connecting a crank chamber and a rocker arm chamber in the engine. The check valve is disposed in a head gasket that is interposed between a cylinder block and a cylinder head of the engine.
With the breathing device for the combustion engine according to the present invention, as compared with the structure in which the check valve is disposed inside the rocker arm chamber or the crankcase such as in the prior art, the structure around the check valve can be simplified to an extent that is resulted from elimination of the use of any member which would otherwise be required to support the check valve. Accordingly, it is possible to reduce the cost and the size of the combustion engine, with the design limitation on the combustion engine being lessened.
In a preferred embodiment of the present invention, the check valve is in the form of a reed valve that is separate from the head gasket and supported by the head gasket.
This substantially eliminates the use of any special casing and sealing mechanism in the breathing device and, therefore, the number of component parts can advantageously be reduced, resulting in further reduction in cost.
In another preferred embodiment of the present invention, the check valve has a longitudinal axis and also has a support portion and a flapper portion opposite to the support portion, in which the support and flapper portions occupy respective positions on the longitudinal axis of the check valve and spaced apart from each other. The check valve has an elongate slot defined therein so as to extend in a direction perpendicular to the longitudinal axis thereof.
Where the breathing device is constructed in this way, the rigidity of the check valve can be sufficiently lowered by the slot with no need to increase the length of the check valve and, therefore, the check valve can have an increased response to opening or closing with small size. Since the check valve can be made in small size in this manner, the check valve can easily be disposed in the head gasket where a space is limited for interposition thereof between the cylinder block and the cylinder head. Also, where the check valve is mounted on the head gasket with the support portion thereof fixedly secured to the head gasket by a fixing member, such as a rivet, the presence of the elongate slot is effective to minimize reduction in sealability which would otherwise occur when the check valve warps, and any possible increase of the rigidity can advantageously be avoided, which would occur as a result of deformation of the support portion of the check valve to a concave shape in a transverse section.
In a further preferred embodiment of the present invention, the head gasket has a portion confronting an intermediate portion of the check valve generally intermediate between the support and flapper portions, which portion of the head gasket is formed with a recess that defines a space between it and the check valve.
In such case, because of the presence of the recess defined in the portion of the head gasket confronting the intermediate portion of the check valve, it is possible to avoid any possible sticking of the check valve to the head gasket by the effect of the viscosity of the oil component.
In a still further preferred embodiment of the present invention, the check valve is formed integrally with a section of the head gasket.
Formation of the check valve integrally with the head gasket makes it possible for a valve mechanism of the breathing device to be simplified in structure along with reduction in number of component parts used.
In a still further preferred embodiment of the present invention, a stopper is defined in the cylinder head for regulating an opening of the check valve. Since the stopper for regulating the opening of the check valve is formed on the cylinder head, no element functionally corresponding to the stopper is needed to be formed separately, resulting in simplification of the structure.
In a still further preferred embodiment of the present invention, the head gasket is in the form of a metallic plate coated with a rubber material. The use of this head gasket is effective to increase the sealability between the check valve and the head gasket.